Transformations: Fix variable interpolation when Scenes is disabled (#101438)

Co-authored-by: Dominik Prokop <dominik.prokop@grafana.com>

.betterer.results

@@ -142,6 +142,14 @@ exports[`better eslint`] = {
     "packages/grafana-data/src/transformations/standardTransformersRegistry.ts:5381": [
       [0, 0, 0, "Unexpected any. Specify a different type.", "0"]
     ],
+    "packages/grafana-data/src/transformations/transformDataFrame.ts:5381": [
+      [0, 0, 0, "Unexpected any. Specify a different type.", "0"],
+      [0, 0, 0, "Unexpected any. Specify a different type.", "1"],
+      [0, 0, 0, "Unexpected any. Specify a different type.", "2"],
+      [0, 0, 0, "Unexpected any. Specify a different type.", "3"],
+      [0, 0, 0, "Unexpected any. Specify a different type.", "4"],
+      [0, 0, 0, "Unexpected any. Specify a different type.", "5"]
+    ],
     "packages/grafana-data/src/transformations/transformers/nulls/nullInsertThreshold.ts:5381": [
       [0, 0, 0, "Unexpected any. Specify a different type.", "0"],
       [0, 0, 0, "Unexpected any. Specify a different type.", "1"]

packages/grafana-data/src/transformations/transformDataFrame.ts

@@ -12,6 +12,9 @@ import {
 import { getFrameMatchers } from './matchers';
 import { standardTransformersRegistry, TransformerRegistryItem } from './standardTransformersRegistry';
 
+// when running within Scenes, we can skip var interpolation, since it's already handled upstream
+const isScenes = window.__grafanaSceneContext != null;
+
 const getOperator =
   (config: DataTransformerConfig, ctx: DataTransformContext): MonoTypeOperatorFunction<DataFrame[]> =>
   (source) => {
@@ -24,11 +27,20 @@ const getOperator =
     const defaultOptions = info.transformation.defaultOptions ?? {};
     const options = { ...defaultOptions, ...config.options };
 
+    const interpolated = isScenes
+      ? options
+      : deepIterate(options, (v) => {
+          if (typeof v === 'string') {
+            return ctx.interpolate(v);
+          }
+          return v;
+        });
+
     const matcher = config.filter?.options ? getFrameMatchers(config.filter) : undefined;
     return source.pipe(
       mergeMap((before) =>
         of(filterInput(before, matcher)).pipe(
-          info.transformation.operator(options, ctx),
+          info.transformation.operator(interpolated, ctx),
           postProcessTransform(before, info, matcher)
         )
       )
@@ -107,3 +119,21 @@ export function transformDataFrame(
 function isCustomTransformation(t: DataTransformerConfig | CustomTransformOperator): t is CustomTransformOperator {
   return typeof t === 'function';
 }
+
+function deepIterate<T extends object>(obj: T, doSomething: (current: any) => any): T;
+// eslint-disable-next-line no-redeclare
+function deepIterate(obj: any, doSomething: (current: any) => any): any {
+  if (Array.isArray(obj)) {
+    return obj.map((o) => deepIterate(o, doSomething));
+  }
+
+  if (typeof obj === 'object') {
+    for (const key in obj) {
+      obj[key] = deepIterate(obj[key], doSomething);
+    }
+
+    return obj;
+  } else {
+    return doSomething(obj) ?? obj;
+  }
+}